Table 3.
GABA and PS responsiveness of M1 point mutants
|
Subunit |
PS |
GABA |
||
|---|---|---|---|---|
| IC50 (μM) | Slope coefficient | EC50 (μM) | Slope coefficient | |
| X(I265S) |
3.43±0.6 (n=6)a |
1.1±0.1 (n=6) |
49.2±5.8 (n=3) |
0.8±0.1 (n=3) |
| X(I267V) |
17.9±1.4 (n=3)b |
1.1±0.05 (n=3) |
2.9±0.1 (n=3) |
1.4±0.7 (n=3) |
| X(T269V) |
12.4±1.9 (n=3)c |
1.2±0.1 (n=3) |
6.5±0.8 (n=3) |
2.9±0.2 (n=3) |
| X(I270L) |
11.5±0.5 (n=4)b |
1.5±0.1 (n=4) |
0.9±0.2 (n=3) |
1.4±0.7 (n=3) |
| X(V273I) |
11.6±0.5 (n=3)b |
1.0±0.02 (n=3) |
12.1±0.5 (n=3) |
3.0±0.3 (n=3) |
| Y(T257F) |
18.6±0.9 (n=4)b |
1.3±0.06 (n=4) |
1.4±0.5 (n=3) |
0.7±0.07 (n=3) |
| Y(M258L) |
100 (biphasic) |
ND |
249.3±28.5 (n=5) |
1.2±0.03 (n=5) |
| Y(S264A) |
88.7±2.9 (n=4)c |
5.3±1.8 (n=4) |
24.4±3.3 (n=3) |
0.8±0.1 (n=3) |
| Y(T257F/M258L) |
41.5±3.0 (n=4)c |
2.3±0.2 (n=4) |
33.4±2.6 (n=3) |
1.9±0.2 (n=3) |
| Y(T257F/S264A) |
10.6±1.9 (n=4)b,d |
0.9±0.08 (n=4) |
1.2±0.1 (n=3) |
2.6±0.4 (n=3) |
| Y(M258L/S264A) |
100 (biphasic) |
ND |
256.0±37.6 (n=4) |
1.22±0.1 (n=4) |
| Y(I262F/S264A) |
97.6±1.9 (n=4)c |
11.5±0.3 (n=3) |
6.3±2.1 (n=3) |
1.5±0.6 (n=3) |
| Y(T257F/M258L/S264A) |
44.4±4.8 (n=4)c |
1.44±0.1 (n=4) |
12.8±1.3 (n=3) |
2.3±0.3 (n=3) |
| X(I265S, Q259N) |
7.7±0.3 (n=4)e |
0.9±0.0 (n=4) |
80.4±10.0 (n=4) |
0.77±0.05 (n=4) |
| UNC-49B-PS7 | 3.3±0.1 (n=4)f,g | 1.0±0.0 (n=4) | 46.2±11.1 (n=4) | 1.06±0.04 (n=4) |
All molecules contained the N305R mutation in the M2–M3 linker. All molecules, apart from X (I265S, Q259N) and UNC-49B-PS7, contained the two conserved UNC-49C residues at positions 259 and 261. Error values are s.e.m. PS IC50 values were determined at EC50 GABA.
Not significantly different from XY (P>0.05, Student's t-test).
Significantly different from XY (P<0.05, Student's t-test).
Significantly different from XY (P<0.05, Mann–Whitney U-test).
Significantly different from Y(T257F) (P<0.05, Student's t-test).
Significantly different from X(I265S) (P<0.05, Mann–Whitney U-test).
Not significantly different from X(I265S) (P>0.05, Mann–Whitney U-test).
Not significantly different from M1-R (P>0.05, Mann–Whitney U-test).